Low flow liquid fuel burner



Aug. 2, 1966 B. J. EISENKRAFT 3,263,732

LOW FLOW LIQUID FUEL BURNER Filed Aug. 10, 1964 Bernard J. B'sen/rraf/ BY %%J.m

ATTORNEY Patented August 2, 1966 3,263,732 LGW FLGW LIQUID FUEL BURNER Bernard J. Eisenlnaft, 1043 E. 81st St., Brooklyn, N.Y. 11236 Filed Aug. 10, 1964, Ser. No. 388,508 5 Claims. (Cl. 158-77) This invention rel-ates generally to fuel burners and, specifically, to a liquid fuel burner employing a vibrating bar for atomization of the liquid fuel prior to combustion and particularly adapted for economical operation at low fuel flow rates.

The use of liquid fuel, such as No. 2 fuel oil, to supply the heating requirements of apparatus such as domestic hot water heaters and, lately, oil-fired air conditioners, is well known. There are periods of substantial duration in the operating cycle of such apparatus wherein the demand for heat is very low, perhaps of the order of about one-half gallon of No. 2 fuel oil per hour, and an example of this is seen in the preparation of hot water for washing in the summertime with the conventional summer-winter hookup for domestic heat and hot water. Conventionally, oil burners employ pressure nozzles for atomization of the liquid fuel and, while these pressure nozzles are perfectly satisfactory for medium and higher flow rates, they do not lend themselves to design for very low flow rates according to the example abovegiven. A pressure nozzle design for medium flow rates would have relatively large orifices which would make for very poor regulation of flow at low flow rates and which, therefore, would not afford the degree of economy of operation that is one of the objects of this invention. Conversely, a pressure nozzle designed for low fuel flow rates would necessarily require orifices of such small size that they would plug readily; moreover, such pressure nozzles would, when operated for medium or greater flow rates of fuel, introduce such a considerable pressure drop into the atomization operation as would decrease overall economy of operation. Much research has been done on the subject of other atomization methods for low flow rates but, until now, no practical substitute has been found for the pressure nozzle.

The present invention comprises a vibrating bar mounted within a spray concentrating cylinder in turn mounted within a burner pipe housing, reservoir means and feed tube means to introduce liquid fuel to the bar in the spray concentrating cylinder, blower means adapted to pass a current of air through the spray concentrating cylinder and burner pipe housing to mix with atomized particles of liquid fuel and form a concentrated stream or spray thereof, electrical circuitry similar to that disclosed in my earlier Patents 2,779,623 and 3,038,532 for maintaining the bar vibrating at a resonant flexural mode, and ignition means for igniting the stream or spray of air and atomized liquid fuel. The feed tube between the reservoir means may be wrapped with a heating coil to raise the temperature of the liquid, decrease its viscosity and increase the tendency of the atomized liquid fuel to vaporize. Extremely fine atomization of the liquid fuel may not be required in all cases and, in these cases, a great deal of power for atomization is likewise not required, the heating of the liquid fuel providing efficient burning of even relatively large droplet to prevent incomplete combustion and smoky combustion gases. With the foregoing, the heating surfaces of the appliance requiring heat will remain cleaner over a longer period of time and thus overall heat transfer is improved. If further heating of the liquid fuel is necessary or desirable, the reservoir itself may be heated by suitable means, and the vibrating bar may also be heated as with an electrical heating element. Gravity flow of liquid fuel from the reservoir to the vibrating bar is preferred, and a feed tube of approximately fl th inch in internal diameter has been found suitable to pass small solid particles without plugging and to permit low flow rates of approximately onc -tenth of a gallon of liquid fuel oil per hour under proper conditions of viscosity. In addition to concentrating the spray or stream of atomized liquid fuel, the concentrating cylinder prevents the spray from contacting the burner pipe housing and accumulating thereon to avoid flashing and smoke.

One of the objects of this invention is to provide apparatus for efficiently atomizing and burning liquid fuel.

Another object of this invention is to provide apparatus for efficiently atomizing and burning liquid fuel at low flow rates.

A further object of this invention is to provide apparatus for atomizing and burning liquid fuel and adapted to supply heat in small or moderate quantities to domestic hot water heaters and other small appliances, which apparatus avoids frequent on-otf operation.

Still another object of this invention is to provide apparatus for concentrating an atomized liquid spray and, specifically, preventing rapid divergence of a spray immediately adjacent the atomizing element.

Yet a further object of this invention is to provide a fuel burner capable of accepting unusual fuels, that is to say capable of accepting, atomizing and burning fuels which are not readily used with conventional pressure nozzles.

Still other and further objects of this invention will become apparent during the course of the following description and by reference to the accompanying drawing and the appended claims.

Referring now to the drawing, in which like numerals represent like parts in the several views:

FIGURE 1 represents a View, generally in vertical elevation and partially broken away to show certain details thereof, and also partially diagrammatic to show certain related electrical circuitry and the fuel reservoir.

FIGURE 2 represents an enlarged view in perspective of the spray concentrating cylinder showing the vibrating bar therein.

Conventional fan or blower 1, having adjustable air inlet 2, is mounted to burner pipe housing 3 through flanged connection 4, the flange bolts being omitted from FIGURE 1 for purposes of clarity. Spray concentrating cylinder 5 is mounted concentrically within burner pipe housing 3 by means of spider elements 6 secured to the said spray concentrating cylinder 5 and engaging the inner walls of said burner pipe housing 3.

Bar 7, rigidly secured as by welding or the like to one end of drive rod 8, is supported by the said drive rod 8 in spray concentrating cylinder 5, longitudinally therein and preferably aligned with the longitudinal axis thereof as shown. Drive rod 8 extends through opening 9 in burner pipe housing 3 and is connected at its upper end to electromechanical transducer 10, the latter being supported on burner pipe housing 3 by mean of supporting members 11.

Electronic circuitry adapted to operate electromechanical transducer 10 and maintain bar 7 vibrating at a resonant flexural mode is represented by block 12 operated by power plug 13. Such electronic circuitry as taught by my earlier US. Patent 2,779,623 may comprise power amplifier 14 electrically connected to electromechanical transducer 10 through Wires 15, preamplifier 16 electrically connected to power amplifier 14 through phase shifter 17, and an electrical pickup electrically associated with and responsive to the vibrations of bar 7 and feeding back electrical signal to preamplifier 16 indicative of the vibrative state of bar 7. As shown in my earlier US. Patent 3,038,532, the electrical pickup may be placed adjacent the point of connection of a drive rod with the vibrating bar, such point obviously being at an antinode. In the preferred embodiment of the present invention, the pickup may be mounted in the same housing with electromechanical transducer 10, operatively associated with the upper end of drive rod 3 which latter may be magnetic, and which clearly corresponds to an antinodal position of bar 7. The feedback from said pickup passes through preamplifier 16 through wires 18. The specific details of the pickup and its location with respect to bar 7 form no part of the present invention and need not, therefore, be described at any greater length.

Liquid fuel in reservoir or tank 19 is introduced to the face of bar 7 bymeans of feed tube 20, the rate of flow being controlled by control valve 21. Where it is anticipated that the viscosity of the liquid fuel must be reduced before atomization, insulated electrical heating element 22 may be wrapped around feed tube 20 and connected to autotransformer 23, the latter being powered by means of power plug 24. It is apparent that the temperature and hence viscosity of liquid fuel flowing through feed tube 20 may be regulated and controlled by autotransformer 23.

Ignition coil 25, which may for convenience be mounted to burner pipe housing 3 as shown, is powered by power plug 26 and provides a continuous arc or spark between electrodes 27.

Assembly of the apparatus may, for instance, comprise inserting spray concentrating cylinder into burner pipe housing 3 from the flanged end thereof, in which event slot 28 in spray concentrating cylinder 5 is provided to permit relative longitudinal movement of said spray concentrating cylinder 5 and drive rod 8 and feed tube 20.

In operation, tank 19 is filled with liquid fuel and valve 21 is opened to permit gravity flow of liquid fuel through feed tube 20 to bar 7 which is maintained vibrating at a resonant fiexural mode by means of the electronic circuitry represented by block 12 according to the teachings of my earlier patents as herein mentioned. Blower 1 takes in air through air inlet 2 and forces the said air through burner pipe housing 3, some of which air passes through spray concentrating cylinder 5 and entrains atomized particles 29 of liquid fuel in a concentrated spray or stream past arcing electrodes 27, causing combustion and flame 30 as shown. Air which flows in the annulus 31 between the inner wall of burner pipe housing 3 and the outer wall of spray concentrating cylinder 5 prevents atomized particles 29 from migrating to the inner walls of burner pipe housing 3 and accumulating thereon which might otherwise cause flashing and smoke.

When higher viscosity liquids and solids such as waxes and naphthalene are to be used as fuel, tank 19 may require heating in addition to the heating of feed tube 20, and bar 7 may also require heating to maintain the fuel in a relatively low state of viscosity before atomization. Bar 7 may be heated by means of electrical elements embedded therein, but the details thereof form no part of the present invention.

When a fuel burner capable of furnishing heat to an appliance slightly in excess of the heat required for proper operation of that appliance is used, a steady state burning condition may be maintained over long periods of time. When a fuel burner furnishes heat greatly in excess of demand, frequent on-oif operation of the burner occurs. In the unsteady state of fuel burner operation, i.e., frequent on-otf operation, combustion efliciency is at its poorest and dirty combustion gases cause fouling of heater surfaces and poor heat transfer. Therefore, where appliances demand low heating rates for extended periods of time, the present invention will provide better operating economy, and will permit these appliances to be heated by fuel oil whereas, at present, they may require other forms of energy such as electricity or gas for low heat demand use.

While I have shown the best embodiment of my invention now known to me, I do not wish to be limited to the exact structure herein described, but may use such substitutes, modifications or equivalents as are embraced within the scope of the specification and claims.

I claim:

1. Liquid fuel burner apparatus comprising:

(a) a cylindrical housing,

(b) a spray concentrating cylinder mounted within said cylindrical housing, the longitudinal axes of said spray concentrating cylinder and said cylindrical housing being parallel to each other, the outer periphery of said spray concentrating cylinder being spaced inwardly of the inner periphery of said cylin drical housing,

(c) an elongated member mounted within said spray concentrating cylinder and adapted to be vibrated at a resonant flexural mode, the longitudinal axes of said member and said spray concentrating cylinder being parallel to each other,

(d) vibrating means to maintain said member vibrating at a resconant flexural mode,

(e) feed means to introduce liquid fuel to a face of said member whereby said liquid fuel is atomized,

(f) blower means mounted to one end of said cylindrical housing to pass a current of air through said cylindrical housing and through said spray concen trating cylinder and between said spray concentrating cylinder and said cylindrical housing, the current of air passing through said spray concentrating cylinder entraining atomized particles of said liquid fuel,

(g) ignition means adjacent the other end of said cylindrical housing in said current of air to ignite said atomized particles of liquid fuel.

2. Liquid fuel burner apparatus comprising:

(a) a circular cylindrical housing,

(b) a spray concentrating cylinder of circular crosssection mounted within said cylindrical housing, the longitudinal axis of said spray concentrating cylinder lying on the longitudinal axis of said cylindrical housing, the outer diameter of said spray concentrating cylinder being less than the inner diameter of said cylindrical housing whereby an annulus is provided between said cylindrical housing and said spray concentrating cylinder,

(0) an elongated member within said spray concentrating cylinder and adapted to be vibrated at a resonant flexural mode, the longitudinal aixs of said member lying on the longitudinal axis of said spray concentrating cylinder,

(d) vibrating means outside said cylindrical housing to maintain said member vibrating at a resonant flexural mode,

(e) a drive rod operatively associated with said vibrating means and extending through said cylindrical housing and through said spray concentrating cylinder and rigidly secured to the central portion of said member,

(f) feed means extending through said cylindrical housing and through said spray concentrating cylinder to introduce liquid fuel to a face of said member whereby said liquid fuel is atomized,

(g) blower means mounted to one end of said cylindrical housing to pass a current of air through said cylindrical housing and through said spray concentrating cylinder and through said annulus between said spray concentrating cylinder and said cylindrical housing, the current of air passing through said spray concentrating cylinder entraining atomized particles of said liquid fuel,

(h) ignition means adjacent the other end of said cylindrical housing in said current of air to ignite said atomized particles of liquid fuel.

3. Apparatus as in claim 2, further comprising:

(i) an electrical heating element wrapped around a portion of said feed means,

(j) an autotransformer supplying electrical energy to said electrical heating element.

4. Liquid fuel burner apparatus comprising:

(a) a cylindrical housing,

(b) an elongated member mounted within said cylindrical housing and adapted to be vibrated at a resonant flexural mode, the longitudinal axes of said member and said housing being parallel to each other,

(c) vibrating means mounted outside said cylindrical housing to maintain said member vibratingat a resonant flexural mode,

(d) drive rod means operatively associated with said vibrating means and extending through said cylindrical 'housing and rigidly secured to the central portion of said elongated member,

(e) feed means to introduce liquid fuel into contact with said member whereby said liquid fuel is atomized,

(f) blower means operatively associated with said cylindrical housing to pass a current of air through said cylindrical housing parallel to the longitudinal axis of said member to entrain atomized particles of said liquid fuel in said current of air,

(g) ignition means adjacent an end of said cylindrical housing in said current of air to ignite said atomized particles of liquid fuel.

5. Liquidfuel burner apparatus comprising:

(a) a cylindrical housing,

(b) an elongated member mounted within said cylindrical housing and adapted to be vibrated at a resonant flexural mode, the longitudinal axes of said member and said housing being parallel to each other,

(c) vibrating means rigidly secured to the central portion of said elongated member to maintain said member vibrating at a resonant flexural mode,

(d) feed means to introduce liquid fuel into contact with said member whereby said liquid fuel is atomized,

(e) blower means operatively associated With said cylindrical housing to pass a current of air through said cylindrical housing parallel to the longitudinal axis of said member to entrain atomized particles of said liquid fuel in said current of air,

(f) ignition means adjacent an end of said cylindrical housing in said current of air to ignite said atomized particles of liquid fuel.

References Cited by the Examiner UNITED STATES PATENTS 3,016,233 1/1962 Olmstead 158-77 3,038,532 6/1962 Eisenkraft 239102 X 3,155,141 11/1964 Doyle et al. 158-77 FREDERICK L. MATTESON, JR., Primary Examiner.

E. G. FAVORS, Assistant Examiner. 

1. LIQUID FUEL BURNER APPARATUS COMPRISING: (A) A CYLINDRICAL HOUSING, (B) A SPRAY CONCENTRATING CYLINDER MOUNTED WITHIN SAID CYLINDRICALD HOUSING, THE LONGITUDINAL AXES OF SAID SPRAY CONCENTRATING CYLINDER AND SAID CYLINDRICAL HOUSING BEING PARALLEL TO EACH OTHER, THE OUTER PERIPHERY OF SAID SPRAY CONCENTRATING CYLINDER BEING SPACED INWARDLY OF THE INNER PERIPHERY OF SAID CYLINDRICAL HOUSING, (C) AN ELONGATED MEMBER MOUNTED WITHIN SAID SPRAY CONCENTRATING CYLINDER AND ADAPTED TO BE VIBRATED AT A RESONANT FLEXURAL MODE, THE LONGITUDINAL AXES OF SAID MEMBER AND SAID SPRAY CONCENTRATING CYLINDER BEING PARALLEL TO EACH OTHER, (D) VIBRATING MEANS TO MAINTAIN SAID MEMBER VIBRATING AT A RESCONANT FLEXURAL MODE, (E) FEED MEANS TO INTRODUCE LIQUID FUEL TO A FACE OF SAID MEMBER WHEREBY SAID LIQUID FUEL IS ATOMIZED, (F) BLOWER MEANS MOUNTED TO ONE END OF SAID CYLINDRICAL HOUSING TO PASS A CURRENT OF AIR THROUGH SAID CYLINDRICAL HOUSING AND THROUGH SAID SPRAY CONCENTRATTRATING CYLINDER AND BETWEEN SAID SPRAY CONCENTRATING CYLINDER AND SAID CYLINDRICAL HOUSING, THE CURRENT OF AIR PASSING THROUGH SAID SPRAY CONCENTRATING CYLINDER ENTRAINING ATOMIZED PARTICLES OF SAID LIQUID FUEL, (G) IGNITION MEANS ADJACENT THE OTHER END OF SAID CYLINDRICAL HOUSING IN SAID CURRENT OF AIR TO IGNITE SAID ATOMIZED PARTICLES OF LIQUID FUEL. 